Regulator



May 17, 1932. L. R. HARNESS ET AL 1,358,271

REGULATOR Filed Dec. 20, 1929 AIAAAAA lAAAAll ATTORNEY Patented May 17, 1932 UNITED STATES PATENT OFFICE SIGN ORS TO WESTINGHOUSE PORATION OF PENNSYLVANIA PENNSYLVANIA, AS-

ELECTRIC AND MANUFACTURING COMPANY, A COR- REGULATOR Application flled December 20, 1929. Serial No. 415,480.

Our invention relates to regulators and it is particularly adapted to be employed for holding the current in an electric circuit constant in spite of large variations in the voltage which gives rise to such current.

During the course of experimental work in connection with the development of viewtransmission systems of the type wherein direct-current amplifiers, comprising a plurality of thermionic tubes, are used at the transmitting end to bring signal impulses up to an amplitude suflicient for satisfactory propagation over wire or radio circuits, it was noted that the said direct-current amplifiers were extremely sensitive to changes in plate and grid potential which were derived from the current utilized for heating the cathodes, in series, of the thermionic tubes. In many instances, even small variations in the voltage of the source supplying cathode-heating current caused appreciable distortion of the output-currents from the amplifier, and large variations in the voltage would entirely spoil the transmission and reception of satisfactory pictures.

Regulators, of many different types heretofore known and utilized for the maintenance of constant current were tried, such regulators being disclosed in the patents to Mayer, 1,353,815, and 1,369,457, the patent to Knoop, 1,487,108, the patent to Knight, 1,654,937, and the patent to Wold, 1,438,976. None of the regulators available to us, however, were sufiiciently sensitive to maintain the cathode-heating current constant, within the extremely narrow limits necessary, and all were discarded as being unsuited for our purpose.

It is, accordingly, an object of our invention to provide a regulator that shall be capable of holding the current in an electric circuit substantially constant, within extremely narrow limits, irrespective of fluctuations in the potential of the source of the said current.

Another object of our invention is to provide a regulator, of the type described, that shall be capable of accurate adjustment within close limits.

Another, and more specific, object of our invention is to provide a regulator, of the type described, that shall be constituted by a lurality of thermionic devices.

11 accordance with our invention, we cause the current which is to be regulated to traverse the space-current path of a thermionic tube or the space-current paths of a plurality of thermionic tubes connected in parallel, and alter the impedance offered by the said path or paths in direct response to any tendency of the current to change from its predetermined value. In order that the alteration of the impedance of the main current-carrying thermionic devices shall be large in proportion to changes in the current, whereby our system shall function satisfactorily, tuations in the potential of the source of current supply, we utilize an additional thermionic device, or a plurality of devices, to amplify the effect of minor current changes and impress the amplified effects upon the control-electrodes of the said main currentcarrying devices to vary the bias-potential thereof.

The novel features that we consider characteristic of our invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of certain specific embodiments, when read in connection with the accompanying drawings, in which:

Figure 1 is a diagrammatic view of a regulator comprising a preferred embodiment of our invention;

Fig. 2 is a diagrammatic view of a regulator comprising an alternative embodiment of our invention;

Fig. 3 is a diagrammatic view of a regulator comprising a further embodiment of our invention that is of particular value in the event that relatively large currents are to be handled; and

Fig. 4 is a diagrammatic view of a regulator comprising yet another embodiment of our invention.

The apparatus illustrated in Fig. 1 comirrespective of relatively great fluctrol-electrode 23.

prises a main electric-discharge device I having an anode 2, a cathode 3 and a control electrode 4. The cathode-heating potential is derived from the secondary winding of a power transformer 5, the primary winding of which is connected to any convenient source of alternating current at commercial frequency. The use of alternating current for heating the cathode is not obligatory or an essential part of our invention, inasmuch as a battery (not shown) may be used for this purpose, if desired.

A source 6, of anode potential, is provided for the electric-discharge device 1, the positive terminal of the source being connected to the anode thereof and the negative terminal being connected to an intermediate point on the secondary winding of the power transformer over a circuit which includes a load 7 and a main impedance device 8, which load and device will, hereinafter, be designated as the load-circuit.

The impedance device is, preferably, constituted by a resistor although it lies w'ithin the scope of our invention to utilize an inductor in lieu thereof.

The control electrode 4 of the main discharge device is connected to a point on the impedance device 8 through a secondary impedance device 10, which may be made variable if desired, and which, preferably, is constituted by a resistor.

The main electric-discharge device is chosen oj/such size that the normal space current therein is amply sufficient for the requirements of the load 7. The load in question may be any power-consuming apparatus which requires constant current, for satisfactory operation.

That portion of our regulator thus far described corresponds, substantially, to the apparatus illustrated in the patent to \Vold, 1,438,976, hereinbefore referred to, and, if extremely close regulation of the current is not necessary, it may be satisfactorily accomplished thereby. If, on the other hand, the current must be kept free from even the most minute variations, regardless of variations of the voltage of the space-current source, additional elements must be added for the purpose of providing a more sensitive control of the impedance of the main electric-discharge device.

Again referring to Fig. 1 of the drawings, more sensitive control of the main electricdischarge device is obtained by connecting an auxiliary electric-discharge device 20 in shunt relation to the resistor 10 which eX- tends between the control electrode 4 and a point on the impedance-device 8 included in the load circuit. The auxiliary dischargedevice, or control-tube, so connected, comprises an anode 21, a cathode 22 and a con- The anode 21 of the auxiliary discharge device is directly connected to the control electrode 4 of the main discharge device, and the cathode 22 thereof is connected to a point on the impedance-device 8 included in the load-circuit.

The control electrode 23 of the auxiliary discharge device 20 is connected to a point in the load-circuit which, by reason of the flow of space currenttherethrough, is maintained at apotential lower than the potential of the intermediate point on the cathodeheating transformer secondary winding to which the main impedance device is connected. A grid-biasing battery 24 may, advantageously, be included between the control-electrode of the control tube and the point on the load circuit to which the grid is connected.

In the operation of the regulator, the normal load-current carried by the main discharge device 1 gives rise to a potential drop a-long the impedance device 8 when flowing through it in the direction of the arrow. The

main grid of the said main discharge device is connected to such point on the impedance device 8 that an increase in current tends to cause the application of a more negative biasing potential to the said grid, whereby the impedance of the main discharge device to the space current therein is increased. At the same time, the grid of the control tube, by reason of its connection to a point on the main impedance-device 8 which is at a higher potential than the point thereon to which the cathode 22 is connected, receives an increment of positive potential with respect to the said cathode and the space-current, in the control tube, increases above the value normally determined by the grid-biasing battery 24.

The increase in space current in the control-tube causes a very appreciable drop in potential across the resistor 10, connected between the grid of the main discharge device and the main impedance device 8, thus rendering the potential of the said grid much more negative with respect to the cathode of the main discharge device 1 than it would he were the drop along the impedance device 8 the only controlling factor.

In other words, by reason of the utilization of the control tube, which functions as an amplifier. the most minute tendency toward a change in the total space current traversing the load is amplified and the effect thereof is imposed upon the grid of the main electricdischarge device 1 to thus alter the impedance of the said device in such direction as to oppose the change.

In an actual regulator, constructed as described, the main electric-discharge device is of the type known commercially as Radiotron UX250 while the control tube is of the type known as Radiotron UX240. The main impedance device 8 has a resistance of 4188 ohms while the secondary impedance amplifier, will now be prises a device 10, connected between the grid of the main discharge device and the said main imedance device, has a resistance of 1 megohm. Vhen using the regulator, we have found that the volta e of the space-current source 6 may be varie over a range of at least 300 volts While still maintaining a substantially constant current, at any predetermined value between 20 and 60 milliamperes.

In the event that extremely close regulation is not required, the load may be utilized as a part of the main impedance device, or it may be substituted therefor. This modification of our invention is not illustrated.

In order that our disclosure shall be complete, a description of the hereinbefore described current regulator, as it is actually utilized in connection with a direct-current given in connection with Fig. 3 of the drawings.

The apparatus illustrated in Fig. 3 complurality of main electric-discharge devices 30 and 31, each having an anode 32, a cathode 33 and a. control-electrode 34. The anodes are connected, in parallel, to the positive terminal of a space-current source 35, the negative terminal of which is connected, through a load constituted by the cathodes of a plurality of thermionic tubes 36 comprised in an amplifier 37, the cathodes of a plurality of control tubes 38, 40 and 41 and a main impedance-device 42, to an intermediate point on the secondary winding of a cathode-heating transformer 43, to the terminals of which are connected the cathodes 33 of the several main electric-discharge devices.

Each of the control devices has an anode 44, a cathode 45 and a control electrode 46. The anode of the first control tube 38 is directly connected to the grids of the main electric-discharge devices and to a point on the main impedance device 42 through a secondary impedance device 47, which may take the form of a resistor. The grid of the first control tube is connected to the anode of the second control tube 40 and to another point on the main impedance device 42 through a secondary impedance device 48. The grid of the said first control tube is maintained at a normal negative potential by means of a small biasing battery 50. The grid of the second control tube 40 is maintained at a normal positive potential by a biasing battery 51 and is connected. through the said battery and a conductor 52, to the anode 44 of the last control device 41.

The conductor 52 is connected, through an impedance device 53, to an intermediate point on impedance-device or resistor 54, included in the cathode-heating circuit between the said second and last control tubes. The grid of the last control tube is maintained at a normal negative potential, with respect to the cathode thereof, by means of,

a biasing battery 55, the positive terminal of which is connected to a point on the resistor 54 in the cathode-heatin circuit.

In the operation of a regu ator system, constructed as illustrated in tendency toward an increase in the space current traversing the main electric-discharge devices occasions a potential drop across the resistor 54, included in the cathodeheating circuit, which causes a partial nullification of the normal negative potential applied to the grid of the last control tube 41. The space current in the said control tube, therefore, increases slightly and, since the said space current gives rise to a potential drop across the resistor 53 connected to the anode of the said tube, the grid of the second control tube 40 tends to become slightly less positive and the space current in the said second control tube diminishes.

A diminution in the space current in the second control tube reduces the potential drop across the resistor 48 connected between the anode thereof, the grid of the first control tube 38 and the main impedance device 42. The grid of the first control device, therefore, becomes considerably more positive than it is normally, and increased current flows in the resistor 47 connected between the anode of the said first'control tube and the main impedance device 42.

The flow of current in the said resistor 47 gives rise to a large voltage drop and, there fore, since the anode of the first control tube and the grids of the main electric-discharge devices 30 and 31 are connected to the negative end of the resistor, the grids of the said discharge devices acquire a highly negative potential in addition to the normal potential applied from resistor 42.

It is not to be inferred, from the foregoing description of a regulator comprising a preferred embodiment of our invention, that the load must, necessarily, be included in series with the main discharge device or devices and the potential source. In fact, the important feature of our invention, namely, the provision of a direct-current amplifier, responsive to minute current changes, for controlling the impedance of the said main discharge device, is applicable to regulator systems that differ widely in superficial aspect. For example, we have found it advantageous, in some instances. to connect the load in parallel with the main discharge dc.- vice and to utilize a thermionic device of the screen-grid type as the control tube.

A regulator system of the parallel-connected type is shown in Fin. 2 of the drawings and comprises a main discharge device (it) having an anode 61, a cathode 62 and acontrol electrode 63. The cathode supplied with energizing current from the secondary winding of a power transformer 64, the primary winding of which is connected to any Fig. 3, any

convenient source of alternating current at commercial frequency.

. A source 65, of current to be regulated, is provided, the )ositive terminal thereof being connected to the anode of the main discharge device 60, and the negative terminal being connected to an intermediate point 66 on the secondary winding of the power transformer over a circuit including an impedance device 67 and a conductor 68.

A control tube 69, of the screen-grid type. having an anode 70, a cathode 71 and a plurality of grids 72 and 7 3, is provided for the purpose of automatically varying the impedance of the main discharge-device in response to variations in potential of the source 65.- The anode of the control tube is connected to the grid of the main discharge device through a grid-biasing battery 74, and anode potential therefor is supplied from the source over a circuit including an impedance device 75 and a load 76 of the type requiring constant current.

One terminal of the cathode of the controltube 69 is directly connected, by the conductor 68, to the intermediate point 66 on the secondary winding of the power transformer, and the other terminal of the cathode is connected, through a resistor 77, to the junction between the load and the impedance device 75. The load, the resistor 77 and the cathode of the control-tube are, accordingly, disposed in shunt relation to the space-current path in the main discharge device 60, with respect to the source 65. Furthermore, the impedance device 75 and the space-current path in the control tube are in shunt relation to the resistor 77 and the cathode of the said control tube.

The control grid 73 of the control tube is connected to an intermediate point 80 on the impedancedevice 67 included between the negative terminal of the source and the secondary winding of the power transformer, while the screen grid 7 2 may be connected to a point on the resistor 77, to the cathode, as indicated by a dotted line 81, or to the conductor connecting the control grid to the impedance device 67, as indicated by a second dotted line 82. The control grid is normally biased positively, with respect to the cathode of the control tube, by a biasing battery 83.

It follows, from a consideration of Fig. 2, in connection with the foregoing description thereof, that, if constant current through the load is to he obtained, the impedance of the main discharge device 60 must "ary inversely with the potential of the source 65, it being assumed that the load, which is connected in shunt relation to the space-current path in the said main discharge device, has a constant impedance. In other words, if the current through the load tends to increase, the impedapce of the main discharge device must be automatically reduced in order that it, in-

stead of the load, shall carry the excess current. The manner in which we obtain automatic variation of the impedance of the main discharge device, through control of the grid potential thereof in response to the varying potential of the source 65, is the essence of.

our invention, and is substantially as follows:

An increase in potential from the source 65 tends to cause an increase in the space current carried by the main discharge device as well as an increase in the current throu h the load. Disregarding, for the moment, t e effect of the normal space current in the control tube, it will be seen that any increase in current through the main discharge device and the load causes the point 80, on the impedance 67, to assume a more negative potential with respect to the cathode of the control tube and to, accordingly, impose a negative bias on the control grid 73. The negative bias, thus applied to the control grid, tends to nullify the positive bias from the battery 83 and to raise the impedance of the control tube to cause decreased space current therein.

A decrease in the normal plate current in the control tube 69 reduces the voltage drop along the impedance device 75, thus giving an increment of positive potential to the grid 63 of the main discharge device and lowering the impedance thereof. By reason of the reduced impedance of the main discharge device, it becomes capable of carrying the excess current and diverting it from the load. A reversal of the sequence of operations takes place when the voltage of the source 65 drops below normal, the impedance of the main discharge device then rising to effectively cause an increase of current through the load.

In certain situations, itis expedient to sacrifice some of the close regulation obtainable with systems of the type just described in order to obtain a system that is less critical in adjustment. Although we are not prepared, at this time, to state positively the reasons why the system, illustrated in Fig. 2 is critical, our experiments have led us to the belief that one of the causative factors is the inclusion of the resistor 77. which supplies plate potential for the tube 69 and a portion of the impedance 67 in the grid-return circuit of the main discharge-device.

We have, accordingly, provided a modified regulator system, illustrated in Fig. 4, whereby ease of adjustment is obtained. at the expense of extremely close regulation, by disassociating the resistor. which determines the plate potential applied to the control tube, entirely from the grid circuit of the main discharge devices.

The apparatus illustrated in Figxtcomprises a plurality of parallel-connected main discharge devices 90 and 91. each having an anode 92, a cathode 93 and a control electrode 94. The cathodes are energized from the secondary winding of a power transformer 95, as in the previously described systems, and the positive terminal of a source 96, to be regulated, is connected to the anodes thereof. The negative terminal of the source 96 is connected, over a circuit including a plurality of impedance devices 97 and 98, to an intermediate point 100 on the secondary winding, and a load 101, that requires constant current, is connected directly between the anodes and the said intermediate point. p

A control-tube 102 is provided, preferably of the pentode type, having an anode 103, a screen-grid 104, a control-grid 105, a cathode 106 and an auxiliary grid 107, interposed between the screen grid and the anode, the auxiliary grid being connected to the cathode.

Cathode potential for the control tube is supplied from the secondary winding of a power transformer 108, and a connection 110 extends between an intermediate point 111 on the said secondary winding and the intermediate point 100 on secondary winding of the power transformer 95 that supplies cathode potential to the main discharge devices, the connection including the impedance device 98.

The screen and control grids of the control tube 102 are joined and are connected, through a biasing battery 112, to an intermediate point 113 on the impedance device 97. In the normal operation of the system, the potential of the biasing battery is so chosen, and the point- 113 on the impedance device is so adjusted, that the positive bias of the battery, is largely nullified by the potential drop along that portion of the impedance device 97 between the point 113 and the point 111 on the secondary winding of the transformer 108.

The anode of the control tube and the grids of the main discharge devices are connected by a conductor 114, and a resistor 115, having a magnitude of approximately 4000 ohms, is connected between the said conductor and the mid point 100 on the secondary winding of the power transformer 95.

When, during the operation of the system described above, the potential of the source 96 tends to increase and, accordingly, to cause an increase in current through the impedance device 97, the resulting potential fall along the said device results in the application of a negative potential to the grids 104 and 105 of the control tube of sufiicient magnitude to entirely overcome the effect of the biasing battery and to bias the said tube negatively to the cut-off point. The consequent decrease in current through the impedance device 115 biases the grids of the main discharge devices more positively and so lowers their impedance that the excess current is taken by them instead of by the load 101. a By reason of the fact that the excess current, as well as the load current, flows in the impedance device 97, the said excess serves to maintain the grid of the control tube at a negative potential, thus keeping the grids of the main discharge devices more positive than normal, just so long as the excess flows.

A diminution of potential of the source 96 is followed by a sequence of operations the reverse of those explained, with the result that the grids of the main discharge devices are maintained more negative than normal during the continuation of the lowered potential. c Although, for purposes of explanation, We have spoken of the current through the load as increasing in response to increased potential, to initiate the regulating operation, the actual increase is almost too slight to be measured, even though the voltage is varied over a range of 100 volts. We are, therefore, justified in stating that, by our system, constant current can be obtained.

It is also important to note that the regulating operation is substantially independent of the cathode temperature of the main discharge device, it having been found, during the course of our experiments, that the cathode potential could be varied from six and one-half volts to a maximum of eight volts Without, appreciably, changing the current through the lead.

A voltage regulator, constructed according to either of the alternative embodiments of our invention described herein, is capable of giving much closer regulation than any similar device, constructed according to the teachings of the prior art, with which we are familiar. Furthermore, our improved regulator is unusually stable in operation, regardless of minor changes in the filament current in the main discharge devices, and, after it has once been calibrated and adjusted, it will remain in adjustment for a period depending, principally, upon the life of the discharge-devices utilized.

Although we have illustrated and described certain specific embodiments of our invention, numerous modifications thereof Will be apparent to those skilled in the art to which it pertains. Our invention, therefore, is not to be limited except insofar as is necessitated by the prior art or by the spirit of the appended claims.

e claim as our invention:

1. An electric circuit comprising an electric-discharge device having an anode, a cathode and a control electrode, a source of space current for said device, an impedance device in series with said source, said anode and said cathode, an impedance device connected between said control electrode and the first-mentioned impedance device, and an electric-discharge device connected in shunt relation to the second-mentioned impedance device to thereby control the impedance offered to said space-current by the first-mentioned electric-discharge devlce.

2. An electric circuit comprising an electric-dischar e device having an anode, a cathode an a control electrode, a source of space current for said device, an impedance device in series with said source, said anode and said cathode, an impedance device connected between said control electrode and the 10 first-mentioned impedance-device, an electric-discharge device connected in shunt relation to the second-mentioned impedance device and means whereby the im edance of the second-mentioned discharge evice is controlled in response to current changes in the first-mentioned im edance device, whereby amplified effects 0 said current changes are utilized to control the impedance offered by the first-mentioned discharge device to the flow of space current therein and the space current therethrough is maintained substanti ally constant.

3. An electric circuit comprising an electric-discharge device having an anode, a cathode and a control electrode, a source of space current for said device, means, responsive to changes in said space current, for controlling the impedance offered thereto by the o0 electric-discharge device, additional means, responsive to changes in sald s ace current,

for controlling the action of t e first-mentioned means and amplifying means interposed between the first and second-mentioned means. In testimony whereof, We have hereunto subscribed our names this 9th day of December, 1929.

LEROY R. HARNESS.

4o SAMUEL A. BOKOVOY. 

